Importance of Fine Control of Se Flux for Improving Performances of Sb₂Se₃ Solar Cells Prepared by Vapor Transport Deposition

Abstract

Sb2Se3 possesses a quasi‐1D (Q1D) structure, which creates an anisotropic charge transporting behavior in which the carrier transport is very efficient along the Q1D direction, which is beneficial for solar cells as long as the absorber is properly aligned along the preferred orientation. However, Sb2Se3 is prone to form donor‐like defects, such as VSe, that are detrimental to the performance. Therefore, both growth of Sb2Se3 along the preferred orientations and the suppression of the formation of VSe are crucial in achieving Sb2Se3 solar cells with a high efficiency. Herein, the importance of fine control of the extra supply of Se during the deposition of Sb2Se3 in controlling crystallographic orientations and the population of VSe in the Sb2Se3 films is described. This control determines the performance of the resulting solar cells in a superstrate configuration with a CdS buffer. Incorporation of Se during the growth resulted in a larger open‐circuit voltage due to the passivation of VSe. However, an excess supply of Se disrupts the favorable orientation by selenizing the top region of the CdS, and therefore degraded the short‐circuit current. Through the optimization of the extra supply of Se vapor, the power conversion efficiency is improved from 3.7% to 5.2%.

Lone pair driven anisotropy in antimony chalcogenide semiconductors

“…One research direction is the orientation control of Sb 2 X 3 films. 13,14 Based on the understanding that Sb 2 X 3 are composed of one-dimensional (1D) [Sb 4 X 6 ] n ribbons which are held together by vdW forces, [15][16][17][18][19] it has been reported that higher PV efficiency could be achieved when the Sb 2 X 3 films are oriented more perpendicular to the substrate due to more efficient carrier transport along ribbons than between them. 20 Consequently, researchers have focused on tailoring the growth orientation of Sb 2 X 3 films in order to achieve high efficiencies.…”

Vapor Transport Deposition of Sb2(S,Se)3 Solar Cells with Continuously Tunable Band Gaps

“…The vapor transport deposition (VTD) process could be a preferential choice to fabricate antimony chalcogenide films with various band gaps in view of the gained achievements before. − This process was first developed to produce superstrate CdS/Sb 2 Se 3 solar cells by Wen et al and obtained a certified PCE of 7.6% in 2018 . Subsequently, Zhang et al.…”

Does Sb2Se3 Admit Nonstoichiometric Conditions? How Modifying the Overall Se Content Affects the Structural, Optical, and Optoelectronic Properties of Sb2Se3 Thin Films

“…Under these circumstances, it may be possible that the Se surplus is effectively incorporated into the Sb 2 Se 3 structure or else it accumulates at the front interface in the form of elemental Se, as has been suggested elsewhere. 67 − 69 Further research and supporting evidence for verification are required.…”